Coronary artery disease is the most common cause of death in the United States today, and half of the deaths in patients with coronary disease occur suddenly. Primary ventricular tachyarrhythmias appear to precipitate the majority of these events. The group of patients with coronary disease at highest risk for sudden death are those with prior myocardial infarction, left ventricular ejection fractions less than or equal to .40, and spontaneous nonsustained ventricular tachycardia. Prior studies have demonstrated that induction of sustained ventricular tachycardia by programmed ventricular stimulation in this group of patients identifies those specifically at highest risk for sudden death. However, no study to date has demonstrated whether there is any beneficial effect on survival of treating patients in this high risk group who do not have symptoms attributable to arrhythmias. The objective of the proposed study is to test the hypothesis that by treating this highest risk group of patients (those with coronary artery disease, left ventricular ejection fractions less than or equal to .40, spontaneous nonsustained ventricular tachycardia and inducible sustained ventricular tachycardia) with antiarrhythmic therapy guided by electrophysiologic studies, the risk of sudden arrhythmic death and spontaneous sustained ventricular tachycardia can be reduced. The specific aims of the study are to: (1) quantify the risk for arrhythmic death and spontaneous sustained ventricular tachycardia in this patient population. (2) Confirm the low risk for arrhythmic events in patients with ejection fractions less than or equal to .40 with spontaneous nonsustained VT but without inducible sustained VT. (3) Determine whether antiarrhythmic therapy guided by programmed stimulation in this high risk population will reduce the incidence of sudden cardiac death. (4) Determine the independent value of the signal averaged ECG to predict sudden cardiac death and spontaneous sustained VT in this patient populatio We propose a prospective randomized study of patients with documented coronary disease, ejection fractions less than or equal to .40 and asymptomatic nonsustained ventricular tachycardia. After undergoing a baseline electrophysiologic study, patients without inducible sustained VT will be followed in a registry. Patients with inducible sustained VT will be randomized to either receive no specific therapy, or antiarrhythmic therapy guided by serial electrophysiologic studies. Antiarrhythmic therapy will include pharmacologic therapy, and/or implantation of an automatic cardioverter/defibrillator when indicated. Antiarrhythmic drugs will be chosen in a random order. After institution of arrhythmic therapy, patients will be followed as outpatients at 3 month intervals. Approximately 4500 patients will be recruited over a 3 year period and followed for at least 2 years or until one of the following end points is reached: sudden death, cardiac arrest (aborted sudden death), or other deaths. The primary analysis will be to compare the death rates of patients with inducible sustained VT randomized to receive no therapy versus the death rates in the patients given therapy guided by electrophysiologic studies. The death rates in the patients with no inducible VT will be compared with the death rates in the first 2 groups.